/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.groupg.practice.net.telnet;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.time.Duration;
import java.util.StringTokenizer;

import org.apache.commons.net.telnet.EchoOptionHandler;
import org.apache.commons.net.telnet.InvalidTelnetOptionException;
import org.apache.commons.net.telnet.SimpleOptionHandler;
import org.apache.commons.net.telnet.SuppressGAOptionHandler;
import org.apache.commons.net.telnet.TelnetClient;
import org.apache.commons.net.telnet.TelnetNotificationHandler;
import org.apache.commons.net.telnet.TerminalTypeOptionHandler;

/**
 * This is a simple example of use of TelnetClient. An external option handler (SimpleTelnetOptionHandler) is used. Initial configuration requested by
 * TelnetClient will be: WILL ECHO, WILL SUPPRESS-GA, DO SUPPRESS-GA. VT100 terminal type will be subnegotiated.
 * <p>
 * Also, use of the sendAYT(), getLocalOptionState(), getRemoteOptionState() is demonstrated. When connected, type AYT to send an AYT command to the server and
 * see the result. Type OPT to see a report of the state of the first 25 options.
 */
public class TelnetClientExample implements Runnable, TelnetNotificationHandler {
    private static TelnetClient tc;

    /**
     * Main for the TelnetClientExample.
     *
     * @param args input params
     * @throws Exception on error
     */
    public static void main(final String[] args) throws Exception {
        FileOutputStream fout = null;

        if (args.length < 1) {
            System.err.println("Usage: TelnetClientExample <remote-ip> [<remote-port>]");
            System.exit(1);
        }

        final String remoteip = args[0];

        final int remoteport;

        if (args.length > 1) {
            remoteport = Integer.parseInt(args[1]);
        } else {
            remoteport = 23;
        }

        try {
            fout = new FileOutputStream("spy.log", true);
        } catch (final IOException e) {
            System.err.println("Exception while opening the spy file: " + e.getMessage());
        }

        tc = new TelnetClient();

        final TerminalTypeOptionHandler ttopt = new TerminalTypeOptionHandler("VT100", false, false, true, false);
        final EchoOptionHandler echoopt = new EchoOptionHandler(true, false, true, false);
        final SuppressGAOptionHandler gaopt = new SuppressGAOptionHandler(true, true, true, true);

        try {
            tc.addOptionHandler(ttopt);
            tc.addOptionHandler(echoopt);
            tc.addOptionHandler(gaopt);
        } catch (final InvalidTelnetOptionException e) {
            System.err.println("Error registering option handlers: " + e.getMessage());
        }

        while (true) {
            boolean end_loop = false;
            try {
                tc.connect(remoteip, remoteport);

                final Thread reader = new Thread(new TelnetClientExample());
                tc.registerNotifHandler(new TelnetClientExample());
                System.out.println("TelnetClientExample");
                System.out.println("Type AYT to send an AYT telnet command");
                System.out.println("Type OPT to print a report of status of options (0-24)");
                System.out.println("Type REGISTER to register a new SimpleOptionHandler");
                System.out.println("Type UNREGISTER to unregister an OptionHandler");
                System.out.println("Type SPY to register the spy (connect to port 3333 to spy)");
                System.out.println("Type UNSPY to stop spying the connection");
                System.out.println("Type ^[A-Z] to send the control character; use ^^ to send ^");

                reader.start();
                final OutputStream outstr = tc.getOutputStream();

                final byte[] buff = new byte[1024];
                int ret_read = 0;

                do {
                    try {
                        ret_read = System.in.read(buff);
                        if (ret_read > 0) {
                            final String line = new String(buff, 0, ret_read); // deliberate use of default charset
                            if (line.startsWith("AYT")) {
                                try {
                                    System.out.println("Sending AYT");

                                    System.out.println("AYT response:" + tc.sendAYT(Duration.ofSeconds(5)));
                                } catch (final IOException e) {
                                    System.err.println("Exception waiting AYT response: " + e.getMessage());
                                }
                            } else if (line.startsWith("OPT")) {
                                System.out.println("Status of options:");
                                for (int ii = 0; ii < 25; ii++) {
                                    System.out.println("Local Option " + ii + ":" + tc.getLocalOptionState(ii) + " Remote Option " + ii + ":"
                                            + tc.getRemoteOptionState(ii));
                                }
                            } else if (line.startsWith("REGISTER")) {
                                final StringTokenizer st = new StringTokenizer(new String(buff));
                                try {
                                    st.nextToken();
                                    final int opcode = Integer.parseInt(st.nextToken());
                                    final boolean initlocal = Boolean.parseBoolean(st.nextToken());
                                    final boolean initremote = Boolean.parseBoolean(st.nextToken());
                                    final boolean acceptlocal = Boolean.parseBoolean(st.nextToken());
                                    final boolean acceptremote = Boolean.parseBoolean(st.nextToken());
                                    final SimpleOptionHandler opthand = new SimpleOptionHandler(opcode, initlocal, initremote, acceptlocal, acceptremote);
                                    tc.addOptionHandler(opthand);
                                } catch (final Exception e) {
                                    if (e instanceof InvalidTelnetOptionException) {
                                        System.err.println("Error registering option: " + e.getMessage());
                                    } else {
                                        System.err.println("Invalid REGISTER command.");
                                        System.err.println("Use REGISTER optcode initlocal initremote acceptlocal acceptremote");
                                        System.err.println("(optcode is an integer.)");
                                        System.err.println("(initlocal, initremote, acceptlocal, acceptremote are boolean)");
                                    }
                                }
                            } else if (line.startsWith("UNREGISTER")) {
                                final StringTokenizer st = new StringTokenizer(new String(buff));
                                try {
                                    st.nextToken();
                                    final int opcode = Integer.parseInt(st.nextToken());
                                    tc.deleteOptionHandler(opcode);
                                } catch (final Exception e) {
                                    if (e instanceof InvalidTelnetOptionException) {
                                        System.err.println("Error unregistering option: " + e.getMessage());
                                    } else {
                                        System.err.println("Invalid UNREGISTER command.");
                                        System.err.println("Use UNREGISTER optcode");
                                        System.err.println("(optcode is an integer)");
                                    }
                                }
                            } else if (line.startsWith("SPY")) {
                                tc.registerSpyStream(fout);
                            } else if (line.startsWith("UNSPY")) {
                                tc.stopSpyStream();
                            } else if (line.matches("^\\^[A-Z^]\\r?\\n?$")) {
                                final byte toSend = buff[1];
                                if (toSend == '^') {
                                    outstr.write(toSend);
                                } else {
                                    outstr.write(toSend - 'A' + 1);
                                }
                                outstr.flush();
                            } else {
                                try {
                                    outstr.write(buff, 0, ret_read);
                                    outstr.flush();
                                } catch (final IOException e) {
                                    end_loop = true;
                                }
                            }
                        }
                    } catch (final IOException e) {
                        System.err.println("Exception while reading keyboard:" + e.getMessage());
                        end_loop = true;
                    }
                } while (ret_read > 0 && !end_loop);

                try {
                    tc.disconnect();
                } catch (final IOException e) {
                    System.err.println("Exception while connecting:" + e.getMessage());
                }
            } catch (final IOException e) {
                System.err.println("Exception while connecting:" + e.getMessage());
                System.exit(1);
            }
        }
    }

    /**
     * Callback method called when TelnetClient receives an option negotiation command.
     *
     * @param negotiation_code - type of negotiation command received (RECEIVED_DO, RECEIVED_DONT, RECEIVED_WILL, RECEIVED_WONT, RECEIVED_COMMAND)
     * @param option_code      - code of the option negotiated
     */
    @Override
    public void receivedNegotiation(final int negotiation_code, final int option_code) {
        String command;
        switch (negotiation_code) {
        case TelnetNotificationHandler.RECEIVED_DO:
            command = "DO";
            break;
        case TelnetNotificationHandler.RECEIVED_DONT:
            command = "DONT";
            break;
        case TelnetNotificationHandler.RECEIVED_WILL:
            command = "WILL";
            break;
        case TelnetNotificationHandler.RECEIVED_WONT:
            command = "WONT";
            break;
        case TelnetNotificationHandler.RECEIVED_COMMAND:
            command = "COMMAND";
            break;
        default:
            command = Integer.toString(negotiation_code); // Should not happen
            break;
        }
        System.out.println("Received " + command + " for option code " + option_code);
    }

    /**
     * Reader thread: Reads lines from the TelnetClient and echoes them on the screen.
     */
    @Override
    public void run() {
        final InputStream instr = tc.getInputStream();

        try {
            final byte[] buff = new byte[1024];
            int ret_read = 0;

            do {
                ret_read = instr.read(buff);
                if (ret_read > 0) {
                    System.out.print(new String(buff, 0, ret_read));
                }
            } while (ret_read >= 0);
        } catch (final IOException e) {
            System.err.println("Exception while reading socket:" + e.getMessage());
        }

        try {
            tc.disconnect();
        } catch (final IOException e) {
            System.err.println("Exception while closing telnet:" + e.getMessage());
        }
    }
}
